Chemistry Covalent Compounds Packet Name: Hr: Page 1 Chemistry A Covalent Compounds 1
Chemistry Covalent Compounds Packet Name: Hr: Page 2 Worksheet #1- Naming Covalent Compounds The ionic compounds that we have used so far have all contained a metal bonded to a nonmetal. You will now learn how to name compounds and write the formulas for compounds containing nonmetals only. Compounds that consist of nonmetals contain covalent bonds. These elements share electrons in order to become stable. (We will worry about how and why this happens later.) Since these compounds form under a variety of conditions we cannot use oxidation numbers determine their formulas. We must instead use prefixes. These prefixes will also be used in the names of each formula so that you know what how many of each type of element is in the compound. 1 = mono 3 = tri 5 = penta 7 = hepta 9 = nona 2 = di 4 = tetra 6 = hexa 8 = octa 10 = deca Consider NO and N 2 O. If we used the naming method from worksheet #1 then we would call each of these nitrogen oxide. If I told you that you produced a gas called nitrogen oxide in lab then you would not know which one to which I was referring. The correct names are below: N 2 O is called dinitrogen monoxide. NO is called nitrogen monoxide. (Note: I did not call this compound mononitrogen monoxide. We never start a compound with the prefix mono-.) Name the following compounds. Formula N 2 O 4 Name dinitrogen tetraoxide P 4 O 10 GeCl 4 H 2 O BCl 3 SO 2 When you write the formula for compounds that are made up of nonmetals you do not need to look up the oxidation numbers. The prefix becomes the subscript. For example: the formula for dinitrogen trioxide is N 2 O 3. The formula for carbon dioxide is CO 2. Did you notice that carbon does not have a prefix? If there is a compound that is made up of all nonmetals and there is no prefix at the beginning of the name, you are to assume the prefix is mono- and the subscript is one. Write the formulas for the following compounds. Name Formula tetraphosphorus decasulfide P 4 S 10 dichlorine heptaoxide silicon tetrafluoride dinitrogen trioxide carbon monoxide carbon tetrachloride Do not swap and drop! Do not reduce! 2
Chemistry Covalent Compounds Packet Name: Hr: Page 3 Worksheet #2: Introduction to Covalent Bonds A covalent bond is formed between nonmetal atoms. The nonmetals are connected by a shared pair of valence electrons. Remember, nonmetals want to gain valence electrons to reach a stable arrangement. If there are no metal atoms around to give them electrons, nonmetal atoms share their valence electrons with other nonmetal atoms. Since the two atoms are using the same electrons they are stuck to each other in a neutral particle called a molecule. A molecule is a neutral particle of two or more atoms bonded to each other. Molecules may contain atoms of the same element such as N 2, O 2, and Cl 2 or they may contain atoms of different elements like H 2 O, NH 3, or C 6 H 12 O 6. Therefore, covalent bonding is found in nonmetallic elements and in nonmetallic compounds. Covalent bonds are intramolecular forces; that is, they are inside the molecule and hold the atoms together to make the molecule. Covalent bonds are strong bonds and it is difficult and requires a lot of energy to break a molecule apart into its atoms. However, since molecules are neutral one molecule does not have a strong electrical attraction for another molecule. The attractions between molecules are called intermolecular forces and these are weak forces. Covalent substances have low melting points and boiling points compared to ionic compounds or metals. At room temperature, covalent substances are gases, liquids or low melting point solids. They do not conduct electricity as solids or when molten and usually do not conduct when dissolved in water. 1. Define the following terms: a) covalent bond b) molecule c) intramolecular force d) intermolecular force 2. List several properties of covalent compounds. 3
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Chemistry Covalent Compounds Packet Name: Hr: Page 7 Worksheet #3: Drawing Single Covalent Bonds Background info: When atoms of nonmetals bond to each other they share valence electrons and form a covalent bond. When atoms bond they usually have to rearrange their electrons from the positions we pictured in the single atom. The goal is for every atom to have eight electrons around it except for hydrogen which has only two electrons. Hydrogen only forms one single bond; other atoms can form up to four single bonds. When you draw a dot diagram for a molecule you start with the atom that is only in the formula once it will be in the center of the molecule with the other atoms arranged around it. If there are only two atoms it doesn t matter where you start. Draw Lewis dot diagrams for the following molecules. HINT: Carbon, nitrogen, and sulfur are usually the central atom(s) (in the center) surrounded by terminal atoms (surrounding central). Carbon is always a central and hydrogen is always a terminal. When in doubt, put the any single atom in the middle, surrounding it with the element that contains more than one atom. Final Answer Ex: nitrogen triiodide (NI 3 ) Show work here 1. carbon tetrabromide (CBr 4 ) 2. dihydrogen monosulfide (H 2 S) 3. dihydrogen monoselenide (H 2 Se) 4. hydrogen (H 2 ) 7
Chemistry Covalent Compounds Packet Name: Hr: Page 8 Worksheet #3 Continued 1. Draw the bonds below: a) phosphorus triodide (PI 3 ) b) bromine (Br 2 ) c) water (H 2 O) d) ammonia (NH 3 ) 2. EXTRA CHALLENGE: Determine if it is an ionic bond or a covalent bond. Show the work and the final answer Remember: Covalent bonds form between two nonmetals that share electrons. Ionic bonds are formed between a metal and a nonmetal that completely transfer electrons. e) methane (CH 4 ) f) iron (II) oxide (FeO) g) carbon tetrachloride (CCl 4 ) h) phosphorus tribromide (PBr 3 ) i) sodium nitride (Na 3 N) j) hydrochloric acid (HCl) 8
Chemistry Covalent Compounds Packet Name: Hr: Page 9 Worksheet #4: Double AND Triple Bonds There are many types of covalent bonds. So far we have drawn single covalent bonds- when two atoms share one pair of valence electrons. Double bonds can form when a shared single bond alone doesn t satisfy either atoms valence. Double bonds are TWO SHARED PAIRS of electrons for a total of 4 electrons (2 electrons from one atom and 2 from the other). Double bonds are much stronger and bond the atoms closer than a single bond. Ex: carbon dioxide Show work here. Final Answer 1. oxygen (O 2 ) 2. ethene (C 2 H 4 )*** C s are always central and they will link together. Triple bonds can form when 3 pairs of electrons are shared for a total of 6 shared electrons. Typically one atom donates 3 electrons and the other atom donates the other 3. Triple bonds are even stronger than double bonds and the atoms are held even closer together. EX: nitrogen (N 2 ) 3. ethyne (C 2 H 2 ) (remember C's are always central atoms) 9
Chemistry Covalent Compounds Packet Name: Hr: Page 10 Worksheet #4 Continued We have looked at diagrams for ionic compounds and for molecules of covalent substances that contain only single bonds. Many molecules contain double or triple bonds. Ideally an atom is involved in only single bonding that is a more stable arrangement. But, if the atom cannot achieve eight electrons in its valence shell it will become involved in double or triple bonds to reach this stable arrangement. Draw diagrams for the following molecules. 1. Double Bonds: a) oxygen (O 2 ) b). formaldehyde (H 2 CO) * the C s in the middle attach the 2 Hs and the O to it. 2. Triple Bonds: c) nitrogen (N 2 ) d). hydrogen cyanide (HCN) *the carbon is in the middle with the other two attached to it. 3. EXTRA CHALLENGE: RECALL THE DIFFERENCE BETWEEN IONIC AND COVALENT!!! e) N 2 H 2 *** (N goes in the middle) f) C 2 H 6 *** (C s in the middle) g) CF 2 Cl 2 *** (C in the middle, 2 F s and Cl s around it) h) KF i) N 2 F 4 *** (N s in the middle) j) Mg 3 N 2 10
Chemistry Covalent Compounds Packet Name: Hr: Page 11 Worksheet #5 Naming Binary Compounds Review #1 Name the following compounds. If the compound contains a special metal you are to use roman numerals to name it. If the compound contains all nonmetals you are to use the prefixes to name the compound. Otherwise name the metal and then the nonmetal with the ide ending. Formula Name Formula Name ZnTe Zinc telluride Fe 2 Se 3 Iron (III) selenide RaI 2 Cu 3 N NaCl S 3 O 9 Trisulfur nonaoxide Cs 3 P P 2 O 3 Au 2 S BF 3 AgF NO 3 NiO PCl 3 Write the formula for the following compounds. You will not need the column for the symbols with oxidation #s for compounds that are made up of nonmetals. Name Symbols with Formula Name Symbols with Formula oxidation #s (optional) oxidation #s (optional) calcium telluride mercury (I) sulfide strontium phosphide rubidium nitride bismuth(v) selenide lead (IV) bromide silver chloride silicon dioxide XXX francium arsenide carbon monoxide XXX platinum oxide carbon disulfide XXX barium iodide diboron trioxide XXX 1. Define the following: a. compound: b. oxidation number: c. subscript: 2. When do you use roman numerals? 3. When do you use prefixes? 11
Chemistry Covalent Compounds Packet Name: Hr: Page 12 Worksheet #6 Naming Binary Compounds Review #2 The following ionic compounds contain both metals and nonmetals. Name Symbols with Formula Formula Name oxidation #s sodium sulfide NaCl magnesium iodide AlCl 3 silver oxide SrBr 2 rubidium fluoride CoBr 2 Name the following special metals Formula Fe 2 S 3 Bi 3 P 5 Hg 2 O SbN Oxidation Number of the Metal Name (use roman numerals) The following compounds contain special metals. Name Symbols with oxidation #s (optional) Formula Formula Oxidation Number of the Metal copper (I) nitride SnO 2 Name (use roman numerals) lead (IV) chloride Hg 3 P iron (II) sulfide Bi 2 S 3 antimony(v) iodide Sb 2 O 3 The following compounds contain nonmetals only. Name Formula Formula Name (use prefixes) dihydrogen monoxide CO boron trichloride P 4 O 10 dinitrogen monoxide SiO 2 dichlorine heptaoxide N 2 O 3 sulfur hexafluoride CBr 4 12
Chemistry Covalent Compounds Packet Name: Hr: Page 13 Worksheet #7- Naming Binary Compounds Review #3 This review sheet contains all types of compounds that we have learned so far. If you can complete this table with only a periodic table (oxidation numbers only) then you should do well on the naming section of the quiz. Name Symbols with oxidation #s Formula Name Symbols with oxidation #s Formula nickel iodide potassium phosphide calcium phosphide antimony(v) sulfide mercury (I) oxide iron (III) bromide platinum nitride nitrogen monoxide XXX magnesium fluoride diphosphorus trioxide XXX aluminum sulfide carbon tetrachloride XXX chromium telluride sulfur trioxide XXX Write the formula for the following compounds. Use roman numerals where appropriate. Remember that compounds which contain nonmetals only need prefixes. Formula Name Formula Name RaI 2 K 3 P AsO 4 AgI FeS Cu 3 P ZnCl 2 Sb 2 Se 3 MgO BCl 3 PtS SO 3 AuF N 2 O Answer the following questions: 1. The charge on an element in a compound is called 2. Metals are of the staircase 3. Nonmetals are of the staircase. 4. The simplest form of matter is called: 5. The little numbers written below the line in compounds are called: 6. The total charge on any compound is: 7. Chemical combination of two or more elements is called: 8. Used to represent chemical compounds: 13
Chemistry Covalent Compounds Packet Name: Hr: Page 14 Worksheet #8: Covalent Bonding Review Sheet Draw diagrams for the following compounds. a) water (H 2 O) b) sulfur dioxide (SO 2 ) c) nitrogen molecule (N 2 ) d) ammonia (NH 3 ) e) methane (CH 4 ) f) phosphorous trichloride (PI 3 ) g) chlorine molecule (Cl 2 ) h) carbon dioxide (CO 2 ) i) oxygen molecule (O 2 ) j) ethane (C 2 H 6 ) (carbons hook to each other with H s all around) 14